1. Field of the Invention
The present invention relates to movable body drive methods and movable body drive systems, pattern formation methods and apparatus, exposure methods and apparatus, and device manufacturing methods, and more particularly, to a movable body drive method and a movable body drive system that drives a movable body along a substantially two-dimensional plane, a pattern formation method using the movable body drive method and a pattern formation apparatus equipped with the movable body drive system, an exposure method using the movable body drive method, and an exposure apparatus equipped with the movable body drive system, and a device manufacturing method using the pattern formation method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are mainly used.
However, the surface of a wafer serving as a substrate subject to exposure is not always flat, for example, by undulation and the like of the wafer. Therefore, especially in a scanning exposure apparatus such as a scanner and the like, when a reticle pattern is transferred onto a shot area on a wafer by a scanning exposure method, positional information (surface position information) related to an optical axis direction of a projection optical system of the wafer surface is detected at a plurality of detection points set in an exposure area, for example, using a multiple point focal point position detection system (hereinafter also referred to as a “multipoint AF system”) and the like, and based on the detection results, a so-called focus leveling control is performed (refer to, for example, U.S. Pat. No. 5,448,332) to control the position in the optical axis direction and the inclination of a table or a stage holding a wafer so that the wafer surface constantly coincides with an image plane of the projection optical system in the exposure area (the wafer surface is within the focal depth of the image plane).
Further, with the stepper or the scanner or the like, wavelength of exposure light used with finer integrated circuits is becoming shorter year by year, and numerical aperture of the projection optical system is also gradually increasing (higher NA), which improves the resolution. Meanwhile, due to shorter wavelength of the exposure light and higher NA in the projection optical system, the depth of focus is becoming extremely small, which caused a risk of focus margin shortage during the exposure operation. Therefore, as a method of substantially shortening the exposure wavelength while substantially increasing (widening) the depth of focus when compared with the depth of focus in the air, the exposure apparatus that uses the immersion method has recently begun to gather attention (refer to, for example, U.S. Patent Application Publication No. 2005/0259234).
However, in the exposure apparatus using this liquid-immersion method or other exposure apparatus whose distance (working distance) between the lower end surface of the projection optical system and the wafer is small, it is difficult to place the multipoint AF system in the vicinity of the projection optical system. Meanwhile, in the exposure apparatus, in order to realize exposure with high precision, realizing surface position control of the wafer with high precision is required.
Further, with the stepper or the scanner or the like, position measurement of the stage (the table) which holds a substrate (for example, a wafer) subject to exposure is performed in general, using a laser interferometer having a high resolution. However, the optical path length of the laser interferometry beam which measures the position of the stage is around several hundred mm or more, and furthermore, due to finer patterns owing to higher integration of semiconductor devices, position control of the stage with higher precision is becoming required. Therefore, short-term variation of measurement values which is caused by temperature fluctuation (air fluctuation) of the atmosphere on the beam optical path of the laser interferometer can no longer be ignored.
Therefore, it can be considered that position control of the table in the optical axis direction and in a tilt direction with respect to the surface orthogonal to the optical axis, including the focus leveling control of the wafer during exposure, using a detection device which detects the surface position information of the table, is to be performed, separately from the interferometer, or together with the interferometer. However, in such a case, the position and the tilt of the table in the optical direction covering the entire movement range at least at the time of exposure of the table has to be measurable, and in order to prevent a sudden change in the position and attitude of the table during the movement, for example, transition between detection values in neighboring detecting positions will have to be performed smoothly.